1. Field of the Invention
The present invention relates generally to train control systems and, in particular to a method, system and apparatus for monitoring in a cab signal system of a train, and for ascertaining and verifying the integrity of a cab signal system, detecting the existence of a fault in the cab signal system and/or detecting a signal aspect in the cab signal system.
2. Description of Related Art
In-cab signaling systems are used to provide an operator of a locomotive with information about the signal aspects for the block of track in which the locomotive is operating. According to such known systems, certain sensing devices are situated near a rail in order to pick up low frequency signals that correlate to certain aspects in a locomotive cab. These low frequency signals are processed by a cab signal control unit, and the resultant information and data is then sent to a cab signal aspect display unit for viewing by the operator. Normally, the signal aspect is indicated to the operator of the train through the use of lamps, e.g., an incandescent lamp, light emitting diode, etc., with each lamp corresponding to a specific signal aspect. Specific train control decisions and operations must be implemented, whether manually or automatically, based upon the provided indication of the signal aspect. Accordingly, the integrity of the entire cab signal system is deemed to be very important, as it conveys safety critical information to the operator, which is vital for safe train operation.
As stated, known cab signal systems are used extensively throughout the railroad industry and represent units that are presently installed on numerous trains and locomotives. The signal aspect information, which is indicated to the operator using the lamps, is also required for use in effectively operating a train control unit or train control system, such as the Electronic Train Management System (ETMS) of Wabtec. Therefore, this signal aspect information must be conveyed to a train control unit, which may not be easily integrated with the cab signal control unit. Therefore, other manners of obtaining or determining this signal aspect data are useful, especially in situations where the cab signal system is already installed and operating on the train.
According to the prior art, there are various methods, apparatus and systems available for monitoring and detecting cab signal conditions, as well as for detecting faults or outage in lights, indicators, flashers, displays, bulbs and the like. For example, see U.S. Pat. Nos. 7,154,403 to Davenport et al.; 7,123,165 to Davenport et al.; 7,098,774 to Davenport et al.; 4,349,810 to Kugo et al.; 6,763,290 to Johnson; 6,624,638 to St-Germain; 6,597,179 to St-Germain; 6,369,704 to Hilleary; 6,349,248 to Dean et al.; 4,314,234 to Darrow et al.; 4,259,659 to Ariyoshi et al.; and 4,068,216 to Brouwer et al.; and U.S. Publication Nos. 2006/0066447 to Davenport et al.; and 2005/0062481 to Vaughn et al.